ON ENHANCED PROCESS MONITORING USING LINEAR PROFILES

Control chart is a useful device of a statistical process control, used to check the stability of the manufacturing process with an objective to detect unfavorable variations in the location and scale parameter of the process. Initially, control charts are used to monitor manufacturing process but now they are extensively used in the health sector, education sector, diagnostic laboratories and nuclear engineering. Many of the processes doesnt measure only the single quality characteristics variable. Sometimes, quality characteristic variable is linearly associated with many response variables and to monitor such variable is termed as linear profiling. In the linear profiling, researchers are concerned about the monitoring of three unknown process parameters such as; Intercept, Slope and error variance. Generally, control chart works into two stages named as prospective stage (Phase I) and retrospective stage (Phase II). Prospective stage is used to analysed the unknown parameters of the process and on the base of these estimated parameters (calculated through Phase I), retrospective stage is used to monitor the quality characteristic of the process. So, consistency of the Phase I analysis may increase the reliability of the Phase II study. In this project, we will make an attempt on Phase I analysis under different sampling strategies to enhance the performance of existing control chart about linear profiling. Moreover; we will propose some new control charts for simultaneous monitoring of simple linear profile parameters. We will examine the performance of the stated proposal in terms of probability to signal, average run length and the comparison of its detection ability with its counterparts. Our study will also cover real life application from adhesive manufacturing industry (monitoring the thickness of tape), Electrical processes (Monitoring the charge of Z-source inverter) and semiconductor manufacturing (monitoring the mass flow controller) to explain the significance of the proposal in different disciplines.